KYOTO, Japan — Seven years after it was negotiated, the Kyoto global warming pact went into force Wednesday — imposing limits on emissions of carbon dioxide and other gases that many scientists blame for warmer temperatures, melting glaciers and rising oceans.

The agreement, negotiated in Japan’s ancient capital of Kyoto in 1997 and ratified by 140 nations, officially took effect midnight New York time.

It targets carbon dioxide and five other gases that can trap heat in the atmosphere, and are believed to be behind rising global temperatures that many scientists say are already disrupting the Earth’s environment and weather patterns.

Even if fully implemented, Kyoto would cut a projected temperature rise by just 0.1 degrees Centigrade by 2100, according to U.N. figures — tiny compared to scenarios by a U.N. climate panel of an overall rise somewhere between 1.4-5.8C by 2100.

“Kyoto is without doubt only the first step,” said Klaus Toepfer, head of the U.N. Environment Program. “We will have to do more to fight this rapid increase in temperature on our wonderful blue planet Earth. It will be hard work.”

U.S., Australia stay outThe United States, the world’s largest emitter of such gases, has refused to ratify the agreement, saying it would harm the economy and is flawed by the lack of restrictions on emissions by emerging economies China and India.

Interactive: The greenhouse effect
“We have been calling on the United States to join. But the country that is the world’s biggest emitter has not joined yet, and that is regrettable,” Japan’s top government spokesman, Chief Cabinet Secretary Hiroyuki Hosoda, told reporters.

The United States accounts for almost a quarter of greenhouse gas emissions.

Australia, the only other developed nation not to join, defended that decision, with Environment Minister Ian Campbell saying the country was nonetheless on track to cut emissions by 30 percent.

“Until such time as the major polluters of the world including the United States and China are made part of the Kyoto regime, it is next to useless and indeed harmful for a country such as Australia to sign up,” Prime Minister John Howard said in Canberra.

The Kyoto agreement was delayed by the requirement that countries accounting for 55 percent of the world’s emissions must ratify it. That goal was reached last year — nearly seven years after the pact was negotiated — with Russia’s approval.

In a statement, U.N. Secretary-General Kofi Annan said “climate change is a global problem. It requires a concerted global response."

“I call on the world community to be bold, to adhere to the Kyoto Protocol, and to act quickly in taking the next steps," he added. "There is no time to lose.” The Kyoto pact is an adjunct to the 1992 U.N. treaty on climate change.

Different targetsThe Kyoto targets vary by region: The European Union is committed to cutting emissions to 8 percent below 1990 levels by 2012; in the United States, the Clinton administration agreed to a 7 percent reduction but President Bush withdrew from the pact in 2001.

Capturing CO2White House spokesman Scott McClellan said Tuesday that “we are still learning” about the science of climate change. In the meantime, McClellan said, “We have made an unprecedented commitment to reduce the growth of greenhouse gas emissions in a way that continues to grow our economy.”

The State Department said Tuesday that that commitment would mean $5.8 billion in 2005 on research and programs addressing climate change. The administration is particularly interested in funding technology to reduce and capture CO2 emissions.

“While the United States and countries with binding emissions restrictions under the Kyoto Protocol are taking different paths, our destination is the same, and compatible with other efforts,” said Richard Boucher, a spokesman for the State Department.

Kyoto allows nations to trade carbon dioxide quotas and Russia in particular expects to have plenty of spare quotas given the collapse of Soviet-era smokestack industries. That trade could bring it billions of dollars in revenue.

Russia also has access to a new European Union market that enables emitters overshooting their targets to buy emission allocations from those falling below. Carbon dioxide is trading at about 7.33 euros ($9.51) per ton.

Still, most agree the fight against climate change after 2012 hinges on policies by Washington.

Bo Kjellen, a researcher at Britain’s Tyndall Centre, said countries like China or India would feel little incentive to sign up if the United States is exempted. “Kyoto won’t work unless the United States is included after 2012,” he said.